In the field of packaging fruit and vegetable products, there are known combination weighing machines that comprise two transmissions with parallel chains, between which are arranged carriages that are joined to the chains such that the coordinated movement of said chains in the same direction makes the carriages move along a closed path. There are buckets attached to these carriages, and the machines comprise a series of work stations distributed along the path followed by the carriages, and by extension the buckets attached to the carriages, such as a loading station where for example fruit is fed into the buckets; a weighing station where the fruit contained in each bucket is weighed; and an emptying or unloading station where the buckets are emptied.
In so-called combination weighing machines, several buckets are attached to the same carriage, each carriage defining a row of buckets, and at the emptying station there is a selective emptying of the buckets, attached to the same carriage or to different carriages, whose total fruit weight is closest to a predetermined value.
Conventionally, the loading station comprises a series of tilted chutes that are suitable for receiving the fruit, such that in each chute the pieces of fruit are arranged contiguously and in alignment to form a line, moving by the force of gravity until they fall into the buckets. This type of chutes usually include vibration means to help the pieces move along better.
For each container, a predetermined number of pieces of fruit is set to be introduced from said feed chutes, which will vary depending on the type of fruit to handle and the total weight one wishes to package. For this purpose there are known counting devices that make it possible to count the pieces of fruit as they are introduced into the buckets and which, furthermore, once the bucket has been loaded with a required number of pieces of fruit, it is capable to generate a signal to a retention means envisaged to momentarily stop the pieces of fruit from moving along the chute until another empty bucket is situated beneath the outlet of said chute for the next load, and so on.
A known type of devices for counting pieces of fruit is based on the use of mechanical means, such as switches that are pressed by the pieces of fruit through contact as they pass over them.
Another type of counting devices is known, which use photoelectric cells that emit a beam of light that is interrupted by the passage of the pieces of fruit, i.e. the counting takes place when the beam detects the passage of a piece of fruit.
By way of example, Spanish utility model ES258970 describes a counting device comprising three photoelectric cells, each one housed upon a vibrating chute, with their respective reflection mirrors, the chutes being arranged at an incline so that the pieces of fruit distributed in a line fall by the force of gravity into a collection hopper. The light beams of the cells are interrupted by the passage of each of the pieces of fruit once they have left the chutes and fall into the hopper, counting in this way the units collected in the hopper.
This type of device has the drawback that it is not suitable for counting pieces of fruit when they are circulating on the chute, since as the pieces form a contiguous line, i.e. are touching one another, the beam could detect two or more pieces of contiguous fruit as if they were one single object, meaning the beam would not be interrupted, leading to a counting error. As a result, this device is only suitable for counting the pieces of fruit once they have left the chute, i.e. when they fall by gravity into the collection hopper, since it is during the path of the fall that a certain separation appears between the pieces of fruit.
It would be desirable to have a supply device with counting means capable of detecting the passage of pieces of fruit when they are still circulating in the chute, even if they are forming a contiguous line, i.e. even in there is no separation between the pieces as they move over the chute.
Unlike the known solutions that are capable of indicating the number of pieces that are supplied, wherein the counting is done when the pieces leave the chute, a supply device capable of carrying out the counting when the pieces are still in the chute will make it possible to control the exact number of pieces that are supplied and emptied into an associated bucket.
Moreover, there are known retention devices envisaged for interrupting the supply of fruit when a bucket has been loaded with a predetermined number of pieces of fruit. This type of devices use folding vanes, each one associated with the end of a chute, which from above interfere with the path of the pieces of fruit. By way of example, Spanish utility model ES258916 describes a device of this type that comprises a series of pivoting vanes articulated to a transmission mechanism that allows a given vane to descend and retain the piece of fruit in the chute, or to raise up to allow the pieces of fruit to circulate.
This retaining device has the drawback that even though the maximum rotation of the vanes is adjustable, not all pieces have the same dimensions, meaning that larger pieces may get squeezed when the vane enters into contact with them to stop them from passing through.
It would also be desirable to have a supply device capable of interrupting the supply of fruit in coordination with the counting means prepared to carry out the retention operation in an improved manner that guarantees gentle contact with the pieces of fruit to avoid them from potentially being damaged.